/**
    * This file Copyright (c) 2014-2015 Magnolia International
    * Ltd.  (http://www.magnolia-cms.com). All rights reserved.
    *
    *
    * This file is dual-licensed under both the Magnolia
    * Network Agreement and the GNU General Public License.
    * You may elect to use one or the other of these licenses.
    *
   * This file is distributed in the hope that it will be
   * useful, but AS-IS and WITHOUT ANY WARRANTY; without even the
   * implied warranty of MERCHANTABILITY or FITNESS FOR A
   * PARTICULAR PURPOSE, TITLE, or NONINFRINGEMENT.
   * Redistribution, except as permitted by whichever of the GPL
   * or MNA you select, is prohibited.
   *
   * 1. For the GPL license (GPL), you can redistribute and/or
   * modify this file under the terms of the GNU General
   * Public License, Version 3, as published by the Free Software
   * Foundation.  You should have received a copy of the GNU
   * General Public License, Version 3 along with this program;
   * if not, write to the Free Software Foundation, Inc., 51
   * Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   *
   * 2. For the Magnolia Network Agreement (MNA), this file
   * and the accompanying materials are made available under the
   * terms of the MNA which accompanies this distribution, and
   * is available at http://www.magnolia-cms.com/mna.html
   *
   * Any modifications to this file must keep this entire header
   * intact.
   *
   */
  package info.magnolia.config.source.yaml;
  
  import info.magnolia.resourceloader.Resource;
  
  import java.io.IOException;
  import java.io.Reader;
  import java.util.Map;
  
  import javax.inject.Singleton;
  
  import org.yaml.snakeyaml.Yaml;
  import org.yaml.snakeyaml.constructor.AbstractConstruct;
  import org.yaml.snakeyaml.constructor.Constructor;
  import org.yaml.snakeyaml.error.Mark;
  import org.yaml.snakeyaml.error.MarkedYAMLException;
  import org.yaml.snakeyaml.error.YAMLException;
  import org.yaml.snakeyaml.nodes.Node;
  import org.yaml.snakeyaml.nodes.ScalarNode;
  import org.yaml.snakeyaml.nodes.Tag;
  
  /**
   * The {@link YamlReader} reads configuration from a yaml file and returns it as a map representing bean properties.
   */
  @Singleton
  public class YamlReader {
  
      public YamlReader() {
      }
  
      public Map<String, Object> readToMap(final Resource res) throws IOException {
          return (Map<String, Object>) readNoCast(res);
      }
  
      protected Object readNoCast(final Resource res) throws IOException {
          final Yaml yaml = newSnakeYaml(res);
          try (final Reader reader = res.openReader()) {
              return yaml.load(new SpaceCleaningReader(reader));
          } catch (YAMLException ye) {
              // TODO: (maybe) throw typed exceptions that generalize these syntax errors (location in the source, ref to the resource object etc)
              throw new RuntimeException(formatYamlExceptionMessage(res, ye), ye);
          }
      }
  
      protected Yaml newSnakeYaml(Resource res) {
          return new Yaml(new CustomConstructor(this, res));
      }
  
      protected String formatYamlExceptionMessage(Resource res, YAMLException ye) {
          final StringBuilder sb = new StringBuilder();
          sb.append("YAML parsing error in ").append(res);
          if (ye instanceof MarkedYAMLException) {
              final Mark mark = ((MarkedYAMLException) ye).getProblemMark();
              final String snippet = mark != null ? mark.get_snippet() : null;
              final String problem = ((MarkedYAMLException) ye).getProblem();
              if (mark != null) {
                  sb.append(" at line ").append(mark.getLine()).append(", column ").append(mark.getColumn());
              }
              if (snippet != null) {
                  sb.append(":\n");
                  sb.append(snippet);
              }
              if (problem != null) {
                  // TODO SnakeYaml tends to be a bit nasty about this "problem", e.g org.yaml.snakeyaml.scanner.ScannerImpl.fetchMoreTokens() prints the actual char THEN it's representation, so you end up with a big fat actual tab in the message instead of JUST \t(TAB)
                  // See https://code.google.com/p/snakeyaml/issues/detail?id=209
                  sb.append(": ").append(problem.replaceAll("\\s*\\t\\s*", " "));
              }
         } else {
             sb.append(": ").append(ye.getMessage());
         }
 
         return sb.toString();
     }
 
     private static class CustomConstructor extends Constructor {
         public CustomConstructor(YamlReader yamlReader, Resource baseResource) {
             yamlConstructors.put(new Tag("!include"), new IncludeConstruct(/*yaml,*/ yamlReader, baseResource));
         }
     }
 
     private static class IncludeConstruct extends AbstractConstruct {
         private final YamlReader yamlReader;
         private final Resource baseResource;
 
         public IncludeConstruct(YamlReader yamlReader, Resource baseResource) {
             this.yamlReader = yamlReader;
             this.baseResource = baseResource;
         }
 
         @Override
         public Object construct(Node node) {
             if (!(node instanceof ScalarNode)) {
                 throw new IllegalArgumentException("Non-scalar !include: " + node.toString());
             }
 
             final ScalarNode scalarNode = (ScalarNode) node;
             final String path = scalarNode.getValue();
 
             final Resource include = baseResource.getOrigin().getByPath(path);
             try {
                 return yamlReader.readNoCast(include);
             } catch (IOException e) {
                 throw new RuntimeException(e); // TODO
             }
         }
     }
 }